Place the cream in a saucepan with the seeds from the cardamon pods. Heat gently until just bubbling around the edge of the pan, then remove from the heat.
Leave to infuse for 20 minutes or so. Strain to remove the seeds if desired.
Gently reheat the cream, then remove from the heat and stir in the chocolate. Stir constantly until the chocolate has melted.
Then stir in the butter and golden syrup until combined. Refrigerate until required.
To make the macarons
Sieve the ground almonds and icing sugar together. Discard any bits of almond that remain in the sieve. If you have lots, top up with a similar amount of extra ground almonds.
In a clean bowl, beat the egg whites with an electric beater until they form stiff peaks. Beat in the caster sugar, a third at a time, adding the food colour with the third batch.
Then carefully fold in the almond/icing sugar mix, a quarter at a time. Mix it well until it is a smooth but thick batter, and when you drop in a spoonful, it eventually sinks back in to the rest.
Line several baking or pizza trays with parchment. Spoon the mixture into a large piping bag fitted with a 1cm (½ in) wide plain nozzle (or snip off the end off a disposable piping bag).
Gently lift the trays just off the surface and drop down again to remove air bubbles and allow to stand for about 15 minutes.
Preheat the oven to 150°C (140°C/300°F/gas mark 2) and bake in the oven for 15 minutes or until firm. The macarons should lift off the parchment when ready.
Remove from the oven, slide the parchment off the baking tray and leave the macarons to cool.
When cool, sandwich the macarons together with the ganache.
Notes
Store in an airtight container in a cool dry place for up to 3 days. Nutrition information is calculated using an online nutrition database - is approximate and is meant as a guideline only.